Semiconductor devices are used in a variety of electronic applications, such as personal computers, cell phones, digital cameras, and other electronic equipment, as examples. Semiconductor devices are typically fabricated by sequentially depositing insulating or dielectric layers, conductive layers, and semiconductor layers of material over a semiconductor substrate, and patterning the various material layers using lithography to form circuit components and elements thereon.
Solder ball grid arrays are also a technique sometimes used to join substrate, dies or packages, with an array of solder balls deposited on the bonding pads of a first substrate, and with a second substrate, die or package joined at its own bonding pad sites to the first pad via the solder balls. Solder balls may be formed on a pad as liquid solder, and then solidified for additional processing. The environment with the solder balls is subsequently heated to melt the solder balls and the packages compressed to cause the solder balls to contact the upper and lower pads.
In some systems, a trace may be disposed over an upper protective layer, above the passivation layer. Such traces may be referred to as post-passivation interconnects (PPIs). Such PPIs may be used to connect a trace on, for example, a substrate or in a redistribution layer (RDL), to a pad or land below the passivation layer. The mounting pads may have a solder ball as part of a ball grid array, or may have another package connector, permitting a second package to be mounted and still be in electrical communication with the lands below the passivation layer.
Corresponding numerals and symbols in the different figures generally refer to corresponding parts unless otherwise indicated. The figures are drawn to illustrate the relevant aspects of the embodiments and are not necessarily drawn to scale.